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Bit tools.

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This commit is contained in:
John Greb 2015-01-17 15:59:44 +00:00
parent 4d83ca105c
commit cb4352a996
3 changed files with 53 additions and 12 deletions
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36
plugins/channel/lora/lorabits.h Normal file
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@ -0,0 +1,36 @@
/*
Interleaving is "easiest" if the same number of bits is used per symbol as for FEC
Chosen mode "spreading 8, low rate" has 6 bits per symbol, so use 4:6 FEC
*/
// Needs adjusting for different sizes
void interleave(short* inout)
{
int i, index = 6;
short in[index * 2];
for (i = 0; i < index; i++)
in[i] = inout[i];
for (i = 0; i < index; i++) {
inout[i] = (1 & in[0 + i]) | (2 & in[1 + i]) | (4 & in[2 + i])
| (8 & in[3 + i]) | (16 & in[4 + i]) | (32 & in[5 + i]);
in[i + index] = in[i];
}
}
// Same sequence for any size
void make_gray(void)
{
short gray[1<<8];
// short ungray[1<<8];
short k = 0;
for (short i = 0; i < 1<<8; i++) {
gray[i] = k;
// ungray[k] = i;
short r = (i+1) & ~i;
k ^= r;
}
// for (short i = 0; i < 1<<5; i++)
// printf("%x:%x:%x.\n", i, gray[i], ungray[gray[i]]);
}

20
plugins/channel/lora/lorademod.cpp
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@ -40,6 +40,7 @@ LoRaDemod::LoRaDemod(SampleSink* sampleSink) :
m_bin = 0;
m_result = 0;
m_count = 0;
m_header = 0;
loraFilter = new sfft(LORA_SFFT_LEN);
negaFilter = new sfft(LORA_SFFT_LEN);
@ -64,8 +65,8 @@ void LoRaDemod::configure(MessageQueue* messageQueue, Real Bandwidth)
int LoRaDemod::detect(Complex c, Complex a)
{
int i;
float peak;
int i, result, negresult;
float peak, negpeak;
float mag[LORA_SFFT_LEN];
float rev[LORA_SFFT_LEN];
@ -77,18 +78,21 @@ int LoRaDemod::detect(Complex c, Complex a)
// process spectrum every 32 samples
loraFilter->fetch(mag);
negaFilter->fetch(rev);
peak = 0.0f;
m_result = 0;
peak = negpeak = 0.0f;
result = negresult = 0;
for (i = 0; i < LORA_SFFT_LEN; i++) {
if (rev[i]/3 > peak) {
peak = rev[i]/3;
m_result = i;
if (rev[i] > negpeak) {
negpeak = rev[i];
negresult = i;
}
if (mag[i] > peak) {
peak = mag[i];
m_result = i;
result = i;
}
}
if (peak > negpeak) {
m_result = result;
}
return m_result;
}

9
plugins/channel/lora/lorademod.h
View File

@ -25,10 +25,10 @@
#include "util/message.h"
#include "dsp/fftfilt.h"
#define SPREADFACTOR (1<<8)
/* Chosen for number of bins, not symbol length */
#define LORA_SFFT_LEN (128)
#define DATA_BITS (6)
#define SAMPLEBITS (DATA_BITS + 2)
#define SPREADFACTOR (1 << SAMPLEBITS)
#define LORA_SFFT_LEN (SPREADFACTOR / 2)
class LoRaDemod : public SampleSink {
public:
@ -73,6 +73,7 @@ private:
int m_bin;
int m_result;
int m_count;
int m_header;
sfft* loraFilter;
sfft* negaFilter;